Electrical cable



April 4, 1937 LAMBERT 3,312,775

ELECTRI CAL CABLE Filed Dec. 15, 1 965 zi /7 am INVENTOR, HENRYLAMBERT,-

Arr/s.

United States Patent 3,312,775 ELECTRICAL CABLE Henry Lambert, 1026Central Ave., Pawtucket, RI. 02863 Filed Dec. 13, 1965, Ser. No. 513,298Claims. (Cl. 174120) The present invention relates generally to theelectrical art and is more particularly concerned with the provision ofa novel and improved protective sheath for insulated electricalconductors.

It is well known in the art to provide an outer protective sheath forinsulated electric wires, and, in providing such a sheath, manyrequirements and standards must be met. For example, the resultant cablemust meet certain requirements for tensile strength and elongation, aswell as meeting certain minimum requirements for resistance to impactand crushing. In addition, tests for flexibility, dielectric strength,impregnation, moisture absorption, and dripping and flaking must also bemet. Also of importance are its flame-retardant properties and itscapacity to carry current overload.

In order to meet the many and varied tests listed above, the cable, inaddition to having the necessary insulation for the electric conductorsper se, must also have a suitable protective outer sheath. It is withsuch an outer sheath that the instant invention is concerned, it beingunderstood that the function of such an outer sheath is not aninsulation function, but rather is a protective function enabling thecable to meet many of the aforelisted tests.

In providing a protective outer sheath of the character above described,it has been conventional in the art to first cover the insulatedconductors with an inner covering, such as paper, and then to cover thepaper with an extruded vinyl. Although from a functional standpoint aprotective sheath embodying the paper inner layer with the extrudedvinyl outer covering has proven to be satisfactory, it has been foundthat the application of such a protective sheath to insulated conductorsis relatively costly. Not only are separate operations required forfirst covering the insulated conductors with a layer of paper or thelike, but, in addition, the equipment required for extruding a Vinylsheath over the paper-coveredinsulated conductors is complicated andcostly.

It is therefore a primary object of the instant invention to provide aprotective outer sheath for insulated condoctors that is capable ofmeeting all of the aforelisted requirements for sheaths of this type butwhich nevertheless is easier and less expensive to apply to theinsulated electrical conductors.

Another object is the provision of a protective outer sheath forelectric conductors that may be applied to the conductors by usingconventional and existing equipment, thus eliminating the expense ofdesigning and providing special equipment for this purpose.

A further object is the provision of a protectivesheath of the characterdescribed wherein the sheath is in the form of an elongated laminatedtape whereby only one operation is required to properly encase theinsulated conductors so as to meet the aforestated requirements.

Still a further object is the provision of a protective sheath of thecharacter described wherein that part of the inner surface of the sheaththat comes in contact with the conductors is free of adhesive, or atleast substantially so, thus facilitating free stripping of the sheathfrom the conductors.

Other objects, features and advantages of the invention will becomeapparent as the description thereof proceeds when considered inconnection with the accompanying illustrative drawings.

In the drawings which illustrate the best mode presently contemplatedfor carrying out the instant invention:

FIG. 1 is a fragmentary perspective view showing my novel and improvedprotective sheath being applied to cover a plurality of insulatedelectrical conductors;

FIG. 2 is a fragmentary perspective view of a modified form of tape thatmay be used in making a protective sheath in accordance with the instantinvention;

FIG. 3 is a further modification of the tape shown in FIG. 2; and

FIG. 4 is another modified form of tape.

Referring now to the drawings and more particularly to FIG. 1 thereof,there is shown generally at 10 a length of cable comprising a pluralityof electrical conductors 12 and 14, each covered by its own suitableinsulation 16 and 18, which insulation may be of any suitable material,such as vinyl. Located between the wires 12 and 14 is a ground conductor20 also covered with its own insulation 22 which may be of any suitablematerial, such as paper. It will be understood that although FIG. 1illustrates two insulated electrical conductors with an insulated groundconductor therebetween, the instant invention is applicable to a cablehaving one or any number of insulated conductors.

A protective outer sheath 24 is spirally wrapped around the insulatedconductors so as to completely encase and protect the latter in orderthat the resultant cable 10 may meet the various types of requirementsand standards hereinbefore enumerated. As illustrated, the outerprotective sheath 24 comprises three separate elongated tapes 26,although it will be understood that an equally effective sheath could beprovided utilizing one or two tapes as well. It has been found that theuse of three separate ends enables existing equipment to be used forspirally wrapping the sheath 24 around the inner conductors, and hencethe use of three ends is preferred, even though it is not essential.

Each of the tapes 26 is of identical construction and comprises a vinylouter layer 28 to which there is laminated an inner backing 30 of asuitable material, preferably paper. It will be understood that thebacking 30 imparts to the tape 26 certain desired characteristics, suchas resistance to elongation, etc., and hence a critical feature of theinner backing 30 is that it be greatly resistant to elongation, thisbeinga feature which is obviously lacking in vinyl. As Will be noted,the inner backing 30 extends longitudinally for the length of the tape26, but does not cover its entire Width. More specifically, a portion3-2 of the inner surface of the vinyl layer 28 is left exposed, andpreferably this exposed inner surface portion is covered with a pressuresensitive adhesive. Likewise, it is. preferred to cover a portion of theouter surface of the vinyl layer 26 with a pressure sensitive adhesive,as illustrated at 34. It will now be seen that when the tapes 26 arespirally wound around the inner conductors, the unbacked portions 32will overlap the portion 34 of the adjacent spiral wrap covered withpressure sensitive adhesive, whereupon the adhesive on portions 32 and34 will' securely bind and integrate the sheath 24 in a manner thoughtto be apparent. Although it is preferred to utilize pressure sensitiveadhesive at both the areas 32 and 34, it will be obvious that adhesivemay be applied to only one of these areas with satisfactory results. Itwill be equally. obvious that the proportion of tape 26 that is backed,and hence the proportion that is exposed, may be varied. The importantthing is that when the tapes 26 are spirally Wrapped to form the sheath24, the inner surface of the sheath in engagement with the insulatedconductors 12, 14 and 20 will be completely hacked or, at least,substantially so. This is an important consideration in meeting certainof the 6 requirements and standards for protective sheaths of the typewith which the instant invention is concerned.

In some cases, no pressure sensitive adhesive may be used, but ratherthe overlapping portions of the tape may be bound by fusion, such asby-application of heat or a suitable solvent. Where used, however, thistechnique must be employed with caution, since the application of toomuch heat might well result in deleterious effects to the vinyl innerinsulations 1 4 and 16.

Referring now to FIG. 2, a slightly modified form of tape is shown.Specifically, the tape 36 comprises a vinyl outer layer 38 having aninner backing made up of a plurality of longitudinally extending strands40 of Fiberglas or the like in side-by-side relation. Thus, theFiberglas strands 40 function to complement the vinyl layer 38 in thesame manner that the paper backing 30 complements the vinyl layer 28shown and described heretofore. It will again be noted that theFiberglas backing 40 does not cover the entire width of the layer 38,thus leaving a portion 42 exposed, which portion may be covered with apressure sensitive adhesive as discussed hereinbefore. It will beunderstood that the tape 36 is applied to provide a protective sheath inexactly the same manner as hereinbefore described in connection with thetapes 26. It will also be understood that other materials havinggenerally the same binding effect as Fiberglas could be alternativelyused for the backing. Examples of acceptable alternative materials wouldbe nylon and cotton yarn.

The tape 44 shown in FIG. 3 is very similar to the tape 36, the onlydifference being that the Fiberglas backing 46 comprises strands thatinstead of being in sideby-side relation are slightly spaced from eachother. In addition, the overall tape is strengthened by having a fewwidely spaced strands of Fiberglas 48 secured to the unbacked portion 50of the vinyl layer 52. Here again, a pressure sensitive adhesive may beapplied to the unbacked portion 50 for effecting integration of thesheath during spiral winding of the tape 44.

In FIG. 4, another form of m yinvention is shown, wherein by making thevinyl tape 54 of suflicient thickness the desired protectivecharacteristics are achieved without the necessity of providing abacking. Once again, however, a portion of the inner surface of the tape54 is preferably covered with a pressure sensitive adhesive, as at 56,and the outer surface of the tape 54 (not shown) may have a similar edgeportion covered with a pres sure sensitive adhesive in the same mannerthat the'p'ortion 34 of tape 26 is so covered.

While there is shown and described herein certain specific structureembodying the invention, it will be manifest to those skilled in the artthat various modifications and rearrangements of the parts may be madewithout departing from the spirit and scope of the underlying inventiveconcept and that the same is not limited to the particular forms hereinshown and described except insofar as indicated by the scope of theappended claims.

What is claimed is:

1. A cable comprising an insulated conductor, a spiral Wrap in contactwith said insulated conductor consisting of at least one elongated tape,said tape comprising a vinyl outer layer, an inner backing laminated tothe inside surface thereof, said backing extending for the length ofsaid tape but covering only a portion of the Width thereof, said backingbeing of a material characterized by substantially greater resistance toelongation than said vinyl, the unbacked portion of said tapeoverlapping the outer surface of the next-adjacent spiral wrap wherebythe inner surface of said sheath in engagement with said conductor issubstantially completely hacked, and means securing said overlappingportions of said tape to each other to integrate said sheath.

2. The cable of claim 1 further characterized in that said inner backingis paper.

3. The cable of claim 1 further characterized in that said inner backingcomprises longitudinally extending strands of a material havingsubstantially the binding characteristics of glass fibers.

4. The cable of claim 1 further characterized in that saidsecuring meanscomprises a pressure sensitive adhesive.

5. The cable of claim 1 further characterized in that said securingmeans comprises fusion of said overlapping portions.

6. The cable of claim 3 further characterized in that said strands arein side-by-side engagement.

7. The cable of claim 3 further characterized in that said strands areslightly spaced from each other.

8. The cable of claim 3 further characterized in that said unbackedportion of said vinyl layer has a few widely spaced longitudinallyextending strands of the same material adhered thereto.

9. The cable of claim 4 further characterized in that said pressuresensitive adhesive is applied to the unbacked portion of said vinyllayer.

10. The cable of claim 9 further characterized in that said pressuresensitive adhesive is also applied to the outer overlapped surface ofsaid tape.

References Cited by the Examiner UNITED STATES PATENTS LEWIS H. MYERS,Primary Examiner. E. GOLDBERG, Assistant Examiner.

1. A CABLE COMPRISING AN INSULATED CONDUCTOR, A SPIRAL WRAP IN CONTACTWITH SAID INSULATED CONDUCTOR CONSISTING OF AT LEAST ONE ELONGATED TAPE,SAID TAPE COMPRISING A VINYL OUTER LAYER, AN INNER BACKING LAMINATED TOTHE INSIDE SURFACE THEREOF, SAID BACKING EXTENDING FOR THE LENGTH OFSAID TAPE BUT COVERING ONLY A PORTION OF THE WIDTH THEREOF, SAID BACKINGBEING OF A MATERIAL CHARACTERIZED BY SUBSTANTIALLY GREATER RESISTANCE TOELONGATION THAN SAID VINYL, THE UNBACKED PORTION OF SAID TAPEOVERLAPPING THE OUTER SURFACE OF THE NEXT-ADJACENT SPIRAL WRAP WHEREBYTHE INNER SURFACE OF SAID SHEATH IN ENGAGEMENT WITH SAID CONDUCTOR ISSUBSTANTIALLY COMPLETELY BACKED, AND MEANS SECURING SAID OVERLAPPINGPORTIONS OF SAID TAPE TO EACH OTHER TO INTEGRATE SAID SHEATH.